South Korea has replaced its top envoy to six-party talks on North Korea's nuclear program, as diplomatic efforts continue to revive the long stalled negotiations.

The Foreign Ministry said Wednesday that former deputy nuclear negotiator Lim Sung-nam will replace Wi Sung-lac, who has been appointed Seoul's ambassador to Russia.

The talks, involving the two Koreas, the United States, China, Russia and Japan have been stalled since April 2009. Pyongyang staged its second nuclear test weeks later.

North Korea is seeking the immediate resumption of the disarmament talks in exchange for foreign aid. But Seoul and Washington are first demanding that the North take action to show its commitment to ending its rogue nuclear weapons program.